Knife blade mounting for chippers



Nov. 3,1953 c. A. JOHNSON 2,557,723

' KNIFE BL AD E. MOUNTING FOR CHIPPERS Filed Oct; 20, 1950 INVEN TOR.

CM: 4. Jam

QM mm Patented Nov. 3 19$? UNITED STATES PATENT OFFICE KNIFE BLADE MOUNTING FOR CHIPPERS Charles A. Johnson, Berlin, N. H.

Application October 20, 1950, Serial No. 191,265

4 Claims.

This invention relates to chippers and particularly to the type of rotary chippers utilized for reducing logs to chips in preparation for conversion into wood pulp in the pulp industry.

Such chippers comprise a heavy steel disc having knives disposed in recesses and extending radially of the disc, or tangentially with respect to a circle concentric with the disc axis, with their cutting edges projecting beyond the face of the disc. For the purposes of maintenance, the knives are detachably mounted in the recesses. Usually, each blade is provided with spaced slots through which boits are passed to clamp the blades in the recesses in properly adjusted protruding position, all as clearly shown in Ottersland Patent No. 2,299,248.

The primary object of this invention is to provide an improved detachable knife blade mounting for disc chippers. A further object is to provide such a mounting which obviates the necessity of drilling, slotting or otherwise specially shaping the blades to accommodate clamping devices. A further object of the invention is to provide a blade mounting which permits a maximum of blade clamping pressure consistent with the geometric relation of the parts required for disposition of the surfaces forming the cutting edge of the blade to give optimum cutting action with minimum power consumption.

My improved mounting is shown in the accompanying drawing as applied to an 8-knife disc though it will be understood that the invention is equally applicable to a disc having any other number of blades.

In the drawings,

Fig. l is a face view, partially broken away, of a chipper disc showing certain parts associated with one knife blade in dotted lines;

Fig. 2 is an enlarged cross-sectional view taken along the line 2-2 of Fig. 1;

Fig. 3 is an enlarged plan View of one of the elements of the clamping device shown in Fig. 2;

Fig. 4 is a cross-sectional view taken along the line 44 of Fig. 3;

Fig. 5 is an end elevation of the element of Fig. 3; and

Fig. 6 is a plan view of another element of the clamping device shown in Fig. 2.

The heavy steel disc It is provided with suitable recesses as will be hereinafter described for mounting eight knife blades E2 in such manner that the cutting edge [4 of each blade projects beyond the face of the disc it) and'extends over a chip slot l6 which passes through the disc H3.

The chipper disc of Fig. 1 is designed to rotate in use in a counter-clockwise direction with the logs being gravity fed thereto in a conventional known manner at an angle to the face of the disc at a point to the left as shown in Fig. 1 of the axis of the disc. The knives [4 are received in blade receiving recesses 20 which are each separate from the chip slots IE, but closely adjacent thereto. The recesses 29, one of which is shown in Fig. 2, are of V-shaped cross-section and are formed by a leading disc wall 22 and a following disc wall 25 converging inwardly from the face of thedisc. As shown, the surfaces formed by the walls 22 and 2 3 are both angularly related to the face of the disc and are both inclined in the cutting direction of its rotation.

fhe blades Hi are fastened to the disc Iii by means of a wedge-shaped clamping member 35}, shown in more detail in Figs. 3-5 inclusive, and associated fastening means comprising a T-bolt 32 and cooperating nut 34 (Fig. 6)

The clamping member 3t has opposed faces 35 and 38 which bear the same angular relationship as that of the converging disc walls 22 and 2d, and, in the form shown, is provided at its bottom edge, as shown in Fig. 3, with T-shaped bolt-receiving recesses having internal countersinks 42.

The recesses 20 continue backwardiy from the face of the disc into spaced apertures as designed to permit passage of screw-threaded T-bolts 32 to the back of the disc, which, as shown in Fig. 2, is suitably cut away to provide a seating face it for each nut 34, each seating face it being normal to the axis of the aperture it.

With the parts formed as thus described, it can be seen that by setting the bolts in the T- recesses so and then passing the bolts through the apertures it, the wedge-shaped clamping members 3% may be placed in the recess overlying a blade is which, in turn, lies against the disc wall surface 22. The wedge member is then drawn into the recess 212 by revolving the nuts 34 relative to bolts 32 to lock the clamping member 3!] which is so shaped and of such size that, when the clamp 32 firmly wedges the blade [2 against the surface 22, the exposed face 52 of clamping member 39 is disposed inwardly towards the time from the plane of revolution of the cutting edge [4.

In the preferred form of the device, and in order to secure maximum wedging action, the axis of aperture 44 and, therefore the axis of the bolt 32 in fastening position, bear the same angular relation to the face of the disc as the bisector of the angle of intersection of the projections of the opposed surfaces 36 and 38 of the clamping members 39. By reason of such geometry, the pressure exerted by the clamping member 30 against the fiat blade I2 extends over a large area, and provides a clamping pressure far greater than that secured by bolting on the cantilever principle of the Ottersland patent.

Also, it will be seen that no special shaping of the flat blade 12 is required since neither the fastening bolts 32 nor any other element passes through the blade I2.

The T-bolts are made detachable from the clamping member 30 so that clamping membersof different overall depth may be utilized, despending upon the particular thickness of the blade [2.

I claim:

1. A rotary chipper disc having a working face, a knife blade receiving recess in said face, said recess being of V-shaped cross-section and formed by leading and following walls converge ing inwardly from the face of the disc, both of said Walls being angularly related to said disc face and both being inclined in the direction of cutting rotation of said disc, a wedge-shaped blade clamping member having opposed surfaces bearing the same angular relationship as that of said converging walls, said clamping member having an internally countersunk recess on its inner edge, and co-operating fastening means extending from said clamping member through the back wall of said disc and seated in the countersink of said clamping member recess and against aback surface of said disc, respectively for wedging said clamping, member against a fiat blade lying against said leading. angularly related disc wall with the cutting edge of the blade projecting beyond the face of the disc, the exposed face of said clamping member in wedging position being disposed inwardly of the plane. of revolution of said cutting edge in rotation of said disc.

2. A rotary chipper disc as claimed in claim 1,

wherein the axis of said fastening means bisects the angle of intersection of the planes of the opposed surfaces of the clamping member.

3. A rotary chipper disc having a Working face, a knife blade receiving recess in said face, said recess being of V-shaped cross-section and formed by leading and following walls converging inwardly from the face of the disc, both of said walls being angularly related to said disc face and both being inclined in the direction of cutting rotation of said disc, a wedge-shaped blade clamping member having opposed surfaces bearing the same angular relationship as that of said converging walls, and fastening means extending from said'clamping member through the back Wall of said disc and seated against a back surface of said disc for wedging said clamping member against a flat blade lying against said leading angularly related disc wall with the cutting edge of the blade projecting beyond the face of the disc, the exposed face of said clamping member in wedging position being disposed inwardly of the plane of revolution of said cutting edge in rotation of said disc.

4. A rotary chipper disc as claimed in claim 3, wherein the axis of said fastening means has sub,- stantially the same angular relation to the face of the disc as the bi-sector of the angle of intersection of the said opposed surfaces of the clamping member.

CHARLES A. J OHN S O N.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 567,046 Rice Sept. 1, 1896 632,618 Anderson Sept. 5, 1899 901,681 Collet Oct. 20', 1908 1,183,015 Lane et a1. May 16, 1916 2,337,407 Ottersland Dec. 21, 1943 

